The Cisco perimeter switch must be configured to block all packets with any IP options.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-221095	CISC-RT-000350	SV-221095r622190_rule		Medium

Description

Packets with IP options are not fast switched and henceforth must be punted to the switch processor. Hackers who initiate denial-of-service (DoS) attacks on switches commonly send large streams of packets with IP options. Dropping the packets with IP options reduces the load of IP options packets on the switch. The end result is a reduction in the effects of the DoS attack on the switch and on downstream switches.

STIG	Date
Cisco NX-OS Switch RTR Security Technical Implementation Guide	2021-03-29

Details

Check Text ( C-22810r409774_chk )
In Cisco NX-OS, all packets with any header option other than the “source-route” header option are dropped. By default, ipv4 source routing is enabled. Verify that source routing is disabled via the following command: no ip source-route If the switch is not configured to drop all packets with IP option source routing, this is a finding.

Fix Text (F-22799r409775_fix)
Configure the switch to drop all packets with IP option source routing. SW1(config)# no ip source-route SW1(config)# end